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        <p>学Python，看到<a target="_blank" rel="noopener" href="http://www.liaoxuefeng.com/wiki/001374738125095c955c1e6d8bb493182103fac9270762a000/001386819196283586a37629844456ca7e5a7faa9b94ee8000">廖老师的文章</a>，介绍了字符编码的问题，就按照文章的内容进行了测试，得到了不太一样的结果。</p>
<p>不过在看结果之前，先总结一下字符编码的历史背景，捋清楚最常见的三种字符编码ASCII，Unicode和Utf-8的差别。</p>
<h2 id="字符编码发展"><a href="#字符编码发展" class="headerlink" title="字符编码发展"></a>字符编码发展</h2><p>先看这张表：</p>
<figure class="highlight bash"><table><tr><td class="code"><pre><span class="line">字符	ASCII		Unicode			Utf-8</span><br><span class="line">A	01000001	00000000 01000001	01000001</span><br><span class="line">中	x		01001110 00101101	11100100 10111000 10101101</span><br></pre></td></tr></table></figure>

<p>最开始的ASCII只能表示英文和基本的字符，中文是不支持的；</p>
<p>之后的Unicode做了统一处理，无论英文还是其他字符都用2个字节表示，即UCS-2方案，随着世界上各种国家更多字符需要表示，Unicode的2个字节如果无法满足需要，就将采用UCS-4方案，用4个字节表示；</p>
<p>Unicode的问题在于浪费空间，比如普通英文字符，最高8位全是0，鉴于此，产生了Utf-8。Utf-8是对Unicode编码通过一些算法和规则来转换得到的，是变长的编码，英文编码只用1个字节，汉字则是3个字节。</p>
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<h2 id="Python2和Python3默认字符编码"><a href="#Python2和Python3默认字符编码" class="headerlink" title="Python2和Python3默认字符编码"></a>Python2和Python3默认字符编码</h2><p>Python中默认的字符编码可以执行：</p>
<figure class="highlight python"><table><tr><td class="code"><pre><span class="line"><span class="keyword">import</span> sys</span><br><span class="line">sys.getdefaultencoding()</span><br></pre></td></tr></table></figure>

<p>Python2和Python3的输出不同，前者为<code>ascii</code>，后者为<code>utf-8</code>。</p>

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